Dynamic cell bit resolution

Abstract

A system and method, including computer software, is used to write to a flash memory device that includes multiple memory cells. One or more of the memory cells are written at a first resolution corresponding to a first number of bits of data. A signal to write at a second resolution corresponding to a second number of bits of data is received. One or more of the memory cells are written at the second resolution.

1. A method of managing a flash memory device, the method comprising:
 detecting a voltage level from a memory cell, the memory cell storing a charge to a voltage level representing a data value; 
 determining the data value represented by the voltage signal based upon a resolution register corresponding to the memory cell, the resolution register indicating a first number of bits stored in the memory cell; 
 receiving a signal to adjust the resolution register; and 
 adjusting the resolution register to indicate a second number of bits stored in the memory cell upon receiving a signal to adjust the resolution register. 
 
     
     
       2. The method of  claim 1 , further comprising erasing the data stored in the memory cell prior to adjusting the resolution register. 
     
     
       3. The method of  claim 2 , further comprising copying the data stored in the memory cell to a buffer or to another memory cell prior to erasing the data stored in the memory cell. 
     
     
       4. The method of  claim 1 , wherein the first number of bits exceeds the second number of bits. 
     
     
       5. The method of  claim 4 , wherein the memory cell is contained within a page of memory cells, wherein each memory cell in the page of memory cells have identical resolutions. 
     
     
       6. The method of  claim 5 , wherein the signal to adjust the resolution register is triggered by an error condition associated with the page of memory cells. 
     
     
       7. The method of  claim 5 , further comprising erasing information stored in the page of memory cells after receiving a signal to adjust the resolution register. 
     
     
       8. The method of  claim 7 , further comprising:
 copying the information stored in the page of memory cell to another group of memory cells before adjusting the resolution register; and 
 updating a logical addressing software code to indicate the physical location of the data. 
 
     
     
       9. The method of  claim 5 , further comprising:
 adjusting the resolution register of a second page of memory cells to indicate the second number of bits stored in the second page of memory cell; and 
 updating logical addressing code to treat the page of memory cells and the second page of memory cells as a single page of memory cells. 
 
     
     
       10. The method of  claim 1 , wherein the memory cell comprises a NAND flash memory cell. 
     
     
       11. An article of manufacture comprising machine-readable instructions that, when executed, cause operations to be performed, the operations comprising:
 identifying error information associated with a first page of memory cells; 
 determining if the error information meets one or more error criterion; and 
 adjusting one or more resolution registers corresponding to the first page of memory cells from a first resolution to a second resolution based upon determining that the error information meets the one or more error criterion, the first and the second resolutions each defining a plurality of voltage ranges, each voltage range corresponding to a possible data value, the first resolution having more voltage ranges than the second resolution. 
 
     
     
       12. The article of manufacture of  claim 11 , the operations further comprising copying the information stored on the first page of memory cells into a buffer before adjusting the resolution of the first page of memory cells. 
     
     
       13. The article of manufacture of  claim 12 , the operations further comprising recopying the information copied into the buffer into one or more pages of memory cells associated with resolution registers set to the second resolution. 
     
     
       14. The article of manufacture of  claim 11 , wherein the error information comprises a number of errors encountered while accessing the first page of memory cells. 
     
     
       15. The article of manufacture of  claim 14 , wherein determining if the error information meets an error criteria includes determining if the number of errors is greater than a threshold number of errors. 
     
     
       16. The article of manufacture of  claim 11 , the operations further comprising:
 identifying a second page of memory cells that is configured to store data at the second resolution; and 
 updating logical addressing code to treat the first page of memory cells and the second page of memory cells as a single page of memory cells. 
 
     
     
       17. A system for data storage, the system comprising:
 a plurality of memory cells, each memory cell adapted to receive charge during a write operation to a voltage level corresponding to a data value having a specified number of bits; 
 a resolution register associated with the plurality of memory cells, the resolution register including entries each indicating a number of bits stored in one or more corresponding memory cells; and 
 a processor configured to:
 identify error information associated with the plurality of memory cells; 
 determine if the error information meets one or more error criterion; and 
 adjust the resolution register associated with the plurality of memory cells from a first resolution to a second resolution based upon determining that the error information meets the one or more error criterion, the first and the second resolutions each defining a plurality of voltage ranges, each voltage range corresponding to a possible data value, the first resolution having more voltage ranges than the second resolution. 
 
 
     
     
       18. The system of  claim 17 , further comprising a host interface adapted to receive commands from a host device and for exchanging data with the host device. 
     
     
       19. The system of  claim 18 , further comprising a logical addressing software code to translate logical addresses received from the host device into physical addresses to access data. 
     
     
       20. The system of  claim 17 , wherein the plurality of memory cells include NAND flash memory cells.